The invention is concerned with a two-part hipjoint socket for anchoring in the pelvic bone, such that by turning about the polar axis an outer cup may be clamped into the pelvic bone and/or an inner cup be clamped into the outer cup.
Hipjoint sockets of the kind named above are known, for example, from the European patent publications EP-B-0 237 751 and EF-B-0 242 633. In the case of the construction according to the first named EP patent it is a question of a screw socket in which both the outer cup is screwed into the pelvic bone and the inner cup which contains the actual socket cup for receiving the joint head is screwed into the outer cup. The socket according to the second of the above patents is a so-called spreader socket the outer cup of which is slit from the base up to its circumference so that individual flaps arise. By screwing in an inner cup the flaps which are provided on the outside with spikes are widened for anchoring the socket, the spikes penetrating into the bone.
Moreover the practice is known of providing a hipjoint socket or one of its cups at one part of the circumference of the equatorial base with an elevation in order to reduce or avoid the risk of luxations of the joint head under extreme deflections of the joint. In the EP Patent 0 150 198 in order to make "correct" setting of the elevation possible a two-cup socket is shown in which the inner cup carrying the elevation may be inserted in the outer cup in different angular positions. Similarly in the case of the socket according to the EP Patent 0 270 744 an asymmetrical insert may be inserted in different angular positions in an outer cup which maybe screwed in.
Since in the case of outer and/or inner cups which may be located by turning a definite final position of the generally screwed-in part or parts is not provided, it is not possible to locate asymmetries arranged on the outer or inner cups in an optimum angular position in the bone.
The problem of the invention is therefore in the case of sockets of the kind mentioned above initially to enable an optimum angular position of an elevation on the circumference of the base.